Well --- obviously a poll done one day after a person agrees to run in an election is not going to be reliable in any way.
Actually the poll was done the two days prior to his Sunday announcement [Fri & Sat]... However it was reported etc. maybe as early as Thursday that he was going to accept and the announcement press conference scheduled, etc. Thus the word was getting out ...
This poll would be usefull only to the extent to where he is at that time and as a base line of where he needs to place emphasis..... Like shore up the Republican party, female voters, demographics, etc.